“At some point down the line, we may have a way of telling who needs an extra shot, and who doesn’t,” Murthy said on a call hosted by US Health and Human Services’ Covid-19 Community Corps.

“Right now, we don’t have that indicator, which is why we’re recommending that not only people get vaccinated across the board — regardless of whether they were infected in the past or not — but also when it comes to getting these extra doses to sustain and extend your protection, that we do that broadly,” he said.

Even though the doses are not yet available to the public, local health departments nationwide have seen a recent surge in calls from people wanting to make appointments, according to the National Association of County and City Health Departments.

The research, published Friday in the CDC’s Morbidity and Mortality Report, found hospitalizations and emergency room visits for children with Covid-19 increased from June to August. And in the two-week period in mid-to-late August, ER visits were 3.4 times higher in the states with the lowest vaccination rates while hospitalizations were 3.7 times higher than in states with the highest vaccination rates. The states with the lowest vaccination coverage were in the South.

Schools and universities enact safety measures

The risk of Covid-19 spread at schools and campuses remains critical, and recent research demonstrates how unmasked behavior among the unvaccinated can lead to outbreaks.

To prevent similar outbreaks, some universities have instituted mandates to attend classes in-person.

Virginia Tech disenrolled 134 students for failing to comply with the university’s requirement that students be fully vaccinated against Covid-19, and “did not submit vaccination documentation or receive a medical or religious exemption,” according to a statement on Monday.

“Communities with high vaccination coverage are seeing lower pediatric cases and hospitalizations,” CDC director Dr. Rochelle Walensky said.

Along with vaccinations, mask-wearing is also beneficial to curbing Covid-19 spread, evidence shows.

The state of New York will require weekly Covid-19 testing for teachers and other school employees, with an opt-out for those who are vaccinated, and will continue its mask mandate for everybody in a school building, Gov. Kathy Hochul announced Thursday.

New Mu variant is under observation

A new coronavirus variant designated as Mu by the World Health Organization is being monitored as a “variant of interest,” but federal health officials say they don’t consider it immediately dangerous.

On Tuesday, WHO designated the B.1.621 variant as a “variant of interest” because it carries mutations that could help it partially evade vaccines and treatments such as monoclonal antibodies. WHO named it Mu under its system to designate important variants using the Greek alphabet.

“This variant has a constellation of mutations that suggests that it would evade certain antibodies,” Fauci said Thursday of Mu. “Not only monoclonal antibodies, but vaccine and convalescent serum-induced antibodies. But there isn’t a lot of clinical data to suggest that — it is mostly laboratory, in vitro, data.

“Not to downplay it — we take it very seriously. But remember, even when you have variants that do diminish somewhat the efficacy of vaccines, the vaccines still are quite effective against variants of that type. Bottom line, we’re paying attention to it. We take everything like that seriously. But we don’t consider it an immediate threat right now,” he said.

The Delta variant still accounts for more than 99% of Covid-19 cases diagnosed and sequenced in the US, Walensky said Thursday, while Mu is rare.

“We are watching it carefully,” she said.